Nanolithographic printing devices, such as those used in direct write processes like cantilever tip-based deposition processes like DPN® printing, can be operated to apply ink to a nanoscopic tip such as an atomic force microscope (AFM) tip by dipping the tip into inkwells. See for example U.S. Pat. No. 6,827,979 to Mirkin; U.S. Pat. No. 6,642,179 to Liu; U.S. Pat. No. 7,081,624 to Liu; U.S. Pat. No. 7,005,378 to Crocker, regarding printing and U.S. Pat. No. 7,034,854 regarding inkwells. When dipping, it is often necessary to accomplish selective ink delivery to nanoscopic tips without contaminating surrounding tips when using arrays of multiple nanoscopic tips. Also, the ink should coat only the underside of the cantilever, and ink from one inkwell should not migrate to another ink well. Furthermore, conventional nanolithographic printing devices are typically operated so that the nanoscopic tip approaches an inkwell in slow iterations of movement, causing the dipping time for the tip to be extended. Such movements of the nanoscopic tip can be made manually by an operator, which further increases the dipping time. For example, a nanoscopic tip can be manually controlled until the tip is within 2-5 μm of the inkwell surface. Hence, nanoscale dipping can be a complicated process which can require slow processes to be careful. Conventional wisdom would be that one does not want to operate too quickly so high quality can be maintained.
A problem that can occur with conventional nanolithographic printing devices is the wicking of ink. Wicking can occur when ink spreads along the tip, cantilever, and probe of a nanolithographic printing device. This causes an excessive amount of ink to be deposited upon the probe and can lead to contamination. For example, wicking can cause contamination of other probes and inkwells.
FIGS. 1a-1c show wicking during various stages of dipping for a conventional nanolithographic printing device. FIG. 1a is a top and side view of a conventional nanolithographic printing device in which a probe 10 has been positioned above an inkwell 20 so that the tip 12 of the probe 10 can be dipped into the microwell 22, which contains ink 30.
FIG. 1b is a top and side view of the nanolithographic printing device during an initial phase of dipping the probe tip 12 into the microwell 22. In this phase some wicking has occurred, as shown by the area of ink 30 illustrated in the top view of FIG. 1b. Wicking occurs while the probe 10 is dipped into the inkwell 20, allowing ink 30 to spread along the probe 10 and the upper surface of the inkwell 20.
FIG. 1c is a top and side view of the nanolithographic printing device during a later stage in dipping. Wicking has progressed to an advanced degree, as illustrated by the wicking areas 40. As the probe 10 is dipped and allowed to remain in the inkwell 20, wicking can progress, causing ink 30 to flow along the probe 10 and the upper surface of the inkwell 20.